This patch is a cleanup required before refactoring the view layer syncing
process T73411: Fix ViewLayers cache building.
- Remove FIRSTBASE.
- Remove LASTBASE.
- Remove BASACT.
- Remove OBEDIT_FROM_WORKSPACE.
- Replace OBACT with BKE_view_layer_active_object.
- Replace OBEDIT_FROM_VIEW_LAYER with BKE_view_layer_edit_object.